This invention relates to the field of phase array antennas, and more particularly, this invention relates to the field of phase array antennas as applied for satellite communication or terrestrial point-to-point applications.
In U.S. patent application Ser. No. 09/361,082, a planar configured phase array antenna allows a user to select a desired beam angle in a simplified phase array antenna structure that can be mounted on a surface, such as a chimney, arid allows a user to select the beam angle and scan the beam based on the location of the array antenna and the location of a satellite of interest.
This type of phase array antenna solved prior art problems related to the type of applications where terrestrial point-to-point communications links used parabolic antennas mounted on the roof or sides of buildings. Households in residential areas typically use a parabolic antenna to receive electromagnetic waves from a broadcast satellite. Because this type of satellite dish has a beam that points out of a reflector, it must be mounted away from the house in order to tilt the dish and point it at the sky. The dish is sometimes also mounted on the roof or balcony of a house and directed at a satellite. This type of dish antenna typically comprises a reflector, feedhorn element and a converter, with the feedhorn and converter disposed on the focal position of the reflector. In heavy winds, the satellite dish can be broken. Additionally, a parabolic antenna is sometimes unsightly and spoils the aesthetic appearance of many buildings or houses.
A planar antenna can sometimes be used and placed directly on the side of the building or house to add strength to the antenna and also make its appearance more aesthetic. However, if the beam comes directly out of the surface (xe2x80x9con bore sitexe2x80x9d), the antenna will be directed at the building next door when mounted on a vertical surface.
Some microstrip array antennas have been designed to have a beam tilt such that a beam radiated from the antenna is deviated from a direction perpendicular to the plane of the antenna. For example, an antenna could be given a beam tilt of 23 or 27 degrees. The beam Lilt can be obtained by giving phase differences to a plurality of radiating elements that constitute a phase array. An example of such antenna is disclosed in U.S. Pat. No. 5,181,042 to Kaise et al., where a planar microstrip array antenna has a beam tilt that is formed from a plurality of pairs of circularly polarized wave radiating elements.
However, in the Kaise et al. patent, the antenna has one fixed scan angle and the beam scan is fixed in the beam former. No adjustment, or more importantly, selection of possible scan angles is possible.
U.S. Pat. No. 5,189,433 to Stern et al. discloses a slotted microstrip electronic scan antenna where a network of strip lines are mounted on an opposed surface of a dielectric substrate. A scanning circuit is connected to control terminals of circulators for selectively completing a radio frequency transmission path between an input/output stripline and coupling strip lines. Each linear array is directional, having a major lobe and each major lobe is oriented in a different direction. The scanning circuit is periodically switched between the linear arrays, and causes the antenna to scan a region of space via a different major lobe. Although the beam can be scanned, the Stern et al. solution is not a simple low cost implementation, such as could be used for terrestrial point-to-point or TV receive applications where an electrical scan capability would not be required as in the Stern et al. patent.
U.S. Pat. No. 5,210,541 to Hall et al. discloses a patch antenna array having multiple beam-forming capability using a feed network on a microstrip substrate with patches overlaying an upper substrate. Linear series-connected patch arrays are each resonant and may have open circuits at each end. A traveling wave arrangement of feed lines is provided, and in one embodiment, the total number of beams can be generated as twice the number of feed lines. Again, a simplified selectable structure to scan the beam to a desired location such that a user can obtain a desired and scanned beam at a predetermined location is not disclosed.
The antenna structure as disclosed in the ""082 patent application solves the above-mentioned problem by using a planar configured housing that mounts a dielectric substrate layer and other elements of a phase array antenna. The frame supports the housing and is adapted to be placed on a planar support surface, such as a chimney or side of the house. The housing can be rotated relative to the frame for adjusting azimuth. A plug-in card can be inserted within a plug-in card slot and has signal tracks operatively connected to respective signal tracks extending along the substrate layer. Each of the signal tracks within the plug-in card are formed to have a desired phase shift to scan the beam to a desired location.
However, the antennas as described above are planar but are still opaque. This type of antenna could never be mounted on a window without obstructing one""s view.
It is therefore an object of the present invention to provide a planar configured phase array antenna that is optically transparent and adapted for mounting on the surface of a flat surface.
It is still another object of the present invention to provide an optically transparent phase array antenna that allows a user to select the desired beam angle.
In accordance with the present invention, a phase array antenna of the present invention includes a dielectric layer formed of a material that is optically transparent. An electrically conductive and optically transparent ground plane layer is secured on one side of the dielectric layer. An array of optically transparent antenna elements are positioned over the opposing side of the dielectric layer from the ground plane layer. An optically transparent beam forming network is formed on the dielectric layer on the same side as the optically transparent antenna elements and is operatively connected to the array of optically transparent antenna elements.
An optically transparent adhesive layer is formed on the ground plane layer opposite the dielectric layer for adhesively securing the phase array antenna to a surface. The optically transparent beam forming network is formed from indium tin oxide in one aspect of the present invention. In another aspect of the present invention, the beam forming network can comprise microstrip signal tracks, and the antenna elements comprise radiating patch antenna elements. The antenna elements can also comprise slots that are arranged in rows where each beam forming network comprises microstrip signal tracks that extend onto respective slots. A second optically transparent dielectric Layer is formed over the dielectric layer having the attached ground plane layer. An optically transparent conducting layer is formed on the second dielectric layer and has slots formed therein. Each row has a predetermined slot spacing and dimension for receiving a predetermined center operating frequency of a receive signal.
In yet another aspect of the present invention, the plug-in slot is operatively connected to the beam forming network and configured for receiving a plug-in card and connecting to a beam forming network contained within the plug-in card for imparting a desired phase shift and scanning the beam to a desired location. A directional guide indicates direction in which the phase array antenna has been mounted on the surface. This directional guide can include a display that communicates what plug-in card should be received within the plug-in slot.